Consolidated Statement of Changes in Retained Earnings and Accumulated Other Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance				$ 558,165
Net income	$ 12,614	$ 31,931		27,304	$ 44,004
Pension and post-retirement plan adjustments, net of tax of $1,046, $1,267, $3,132, and $4,161 for the three and nine months ended September 30, 2016 and September 30, 2015	2,157	1,894		4,141	3,786
Income attributable to noncontrolling interests	755	(2,252)		1,104	(2,250)
Cumulative effect of the adoption of ASU 2016-16 (Note 2)	(5,915)			(5,915)
Ending Balance	599,629			599,629
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	897,458	858,368	$ 858,553	901,415	858,553
Net income	12,614	31,931		27,304	44,004
Income attributable to noncontrolling interests	(82)		(848)	(359)	(1,170)
Common dividends	(13,359)		(12,338)	(25,804)	(24,264)
Preferred dividends	(10)		(10)	(20)	(20)
Ending Balance	896,621	877,103	858,368	896,621	877,103
Accumulated Other Comprehensive (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(216,892)	(190,580)	(208,199)	(230,246)	(208,199)
Foreign currency translation adjustments	14,123		(15,056)	24,867	(1,108)
Pension and post-retirement plan adjustments, net of tax of $1,046, $1,267, $3,132, and $4,161 for the three and nine months ended September 30, 2016 and September 30, 2015	2,157		1,894	4,141	3,786
Income attributable to noncontrolling interests	837		(756)	1,463	(1,080)
Reclassification from accumulated other comprehensive (loss) into earnings			2,022		4,125
Ending Balance	$ (199,775)	$ (202,476)	$ (190,580)	$ (199,775)	$ (202,476)